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A/C Flush FAQ

Question:
When should the system be flushed?

Answer:
We believe if the a/c system is opened for service, it's a good time to
flush. A clean system minimizes the chance of a comeback. On systems
that utilize an orifice tube, you can usually judge the condition by
looking at the inlet side of the orifice tube screen. If a substantial
amount of debris is found, flushing would be recommended. Likewise,
visual inspection of the refrigerant oil may indicate it's time to
flush.

Answer:No, not with typical solvent flush methods. The
compressor should be removed from the vehicle and the oil drained from
it. You can pour refrigerant oil into the suction port and turn the
compressor hub by hand which will pump clean oil through the
compressor. Remember, compressors don't compress liquids. So, make sure
you rotate the compressor hub by hand enough to ensure you don't liquid
"slug" the compressor.

Answer:
No. Since these are filters which contain desiccant, they are considered normal replacement items.

Question:
Can I flush the hoses and lines?

Answer:If you're sure the solvent that you are using will
not harm rubber or nylon, then it's alright to flush the hoses. Just
make sure that you don't flush trough any hoses that have mufflers
built into them. And also make sure you don't attempt to flush through
the compressor or expansion device.

Question:
I noticed my A/C hoses have mufflers. Can those be flushed?

Answer:
Though many technicians will flush through hose mufflers, it's usually
not considered a good idea. As a general rule, hoses with mufflers
should be replaced instead of flushed. Since the muffler is only used
to reduce noise, some people opt to remove the muffler in order to
salvage the hose.

Question:
Can I flush through the Orifice tube or expansion valve?

Answer:
No. Flushing through the orifice tube or expansion valve is too
restrictive to the flow of solvent. There is one exception of course.
On some Ford models the orifice tube cannot be removed without cutting
the liquid line. We know of technicians who often remove the liquid
line and back flush through it. In theory, back flushing the liquid
line will clean the orifice tube. This is said to work in most cases;
though replacing the liquid line is the preferred method. Remember, a
dirty orifice tube can starve a compressor of oil.

Question:
Should the evaporator be flushed?
Answer:Most would say yes, but some would argue that it's
not worth the extra effort for two reasons. Flush solvents can be very
difficult to remove from some evaporators. Sometimes the risk of not being able
to remove the solvent outweighs the benefit of flushing that component.
Secondly, some would point out that evaporators stay fairly clean
because any dirt floating around the system is captured first by the
receiver drier, then by the inlet screen of the expansion valve. In the
case of an orifice tube system, most debris would be caught by the
orifice tube screens before it could reach the evaporator. While this
is mostly true, systems that use the block style expansion valves have
no inlet screen, and dirt from a ruptured receiver drier could find its
way into the evaporator. Also, oil likes to accumulate in low-lying
areas of the evaporator. If your goal of flushing is to remove dirty
oil, you'll have plenty of it in your evaporator.

Visitor Comments

Comment #1 (Posted by IFIELD AIR CONDITIONING)
I PERSONALLY WILL ALL WAYS FLUSH ALL HOSES/PIPES, EVAPORATOR AND CONDENSOR.
IF YOU ARE USING A TOP QUALITY FLUSHING FLUID THE REMOVAL OF ALL FLUSHING FLUID SHOULD NOT BE A PROBLEM AS IT WILL BOIL OFF WHEN THE SYSTEM IS DEEP VACUUMED. IF IN DOUBT CARRY OUT A TRIPPLE EVACUATION AND BREAK EACH VACUUM CYCLE WITH OFN. THIS METHOD WILL ENSURE NO MOISTURE REMAINS IN THE SYSTEM.

Comment #2 (Posted by Donald J. Ziriax)
What if I flush with freon 113?

Comment #3 (Posted by jim)
When placing a vacuum on the system to dry it out before charging with fresh 134a refrigerent should the engine (compressor) be running?

Comment #4 (Posted by emilio)
break each vacuum with "OFN" WHAT IS OFN?

Comment #5 (Posted by dwwann)
should the evapator and condencer be removed from auto for complete flush as to turn over or lay flat ect.